Pests are annoying to humans for several reasons. Pests include pathogenic organisms which infest mammals and plants; some pests can spread disease as disease vectors. The pathogenic organisms that infest plants and cause economic loss of plant crops include fungi, insects, arachnids, gastropods, nematodes and the like. The pathogenic organisms that infest animals include ticks, mites, fleas, and mosquitoes. Other pests include cockroaches, termites and ants. These and other pests have annually cost humans billions of dollars in crop losses in the case of agricultural pests and in the expense of keeping them under control. For example, the losses caused by pests in agricultural environments include decreased crop yield, reduced crop quality, and increased harvesting costs. In household scenarios, insect pests may act as vectors for diseases and allergic matter.
Over the years, synthetic chemical pesticides have provided an effective means of pest control. For example, one approach teaches the use of complex, organic insecticides, such as disclosed in U.S. Pat. Nos. 4,376,784 and 4,308,279. Other approaches employ absorbent organic polymers for widespread dehydration of the insects. See, U.S. Pat. Nos. 4,985,251; 4,983,390; 4,818,534; and 4,983,389. Use of inorganic salts as components of pesticides has also been tried, as disclosed in U.S. Pat. Nos. 2,423,284 and 4,948,013, European Patent Application No. 462 347, Chemical Abstracts 119(5):43357q (1993) and Farm Chemicals Handbook, page c102 (1987).
However, it has become increasingly apparent that the widespread use of synthetic chemical pesticides has caused detrimental environmental effects that are harmful to humans and other animals. For instance, the public has become concerned about the amount of residual chemicals that persist in food, ground water and the environment, and that are toxic, carcinogenic or otherwise incompatible to humans, domestic animals and/or fish. Moreover, some target pests have even shown an ability to develop resistance to many commonly used synthetic chemical pesticides. In recent times, regulatory guidelines have encouraged a search for potentially less dangerous pesticidal compositions via stringent restrictions on the use of certain synthetic pesticides. As a result, elimination of effective pesticides from the market has limited economical and effective options for controlling pests. As an alternative, botanical pesticides are of great interest because they are natural pesticides, i.e., toxicants derived from plants that are safe to humans and the environment. Use of food-grade plant essential oils have been tried, as described in U.S. Pat. Nos. 5,439,690, 5,693,344, 6,004,569, 6,114,384, and 6,183,767 B1. However, these plant essential oils when used alone can be expensive, impractical or ineffective under certain circumstances.
Accordingly, there is a great need for novel pesticidal compositions containing no pyrethrum, synthetic pyrethroids, chlorinated hydrocarbons, organo phosphates, carbamates and the like, but comprising food-grade plant essential oils, to be used against invertebrate pests, including insects, arachnids, larvae and eggs thereof. In addition, there is a need for a method of treating a locus to be protected to kill and repel invertebrate pests.